Air pressure

[BlackBart]

Why would a 2019 FL need air pressure to start?

I can see it needing air to MOVE if its got a automatic boat anchor tranny, but why wouldn’t it start if its low?

 

[Electric Chicken]

Why would a 2019 FL need air pressure to start?

I can see it needing air to MOVE if its got a automatic boat anchor tranny, but why wouldn’t it start if its low?

Beats me. My Mack can be dead flat 0 PSI. It's also an automated transmission.

 

[InTooDeep]

Beats me. My Mack can be dead flat 0 PSI. It's also an automated transmission.

Same with my 2021 Cascadia DT12. I take couple weeks off all the time. When I get in truck it isn't unusual to have zero air pressure and it still starts

 

[Electric Chicken]

That’s the only way I can think of.

Curious about the 60psi thing, unless the transmission has its own tank. My air goes down below 60 sometimes when being loaded or unloaded, and every time I pump my brakes down or drain my air tanks. Truck always starts.

They always have their own tank but they're kind of all connected anyway. I lose all tank pressures if I sit long enough with the truck off and a forklift constantly playing with my leveling valve just like you do.

Unless I have a check valve somewhere that's defective, it seems normal and it never fails to start even with 0 air pressure (if I park it long enough like these last few weeks it'll all drain out).

My Schneider trucks never failed to start due to lack of air either and they were as old as 2015 with the DT12, and I drove a bunch of different ones that were fully tapped out.

 

[Electric Chicken]

Same with my 2021 Cascadia DT12. I take couple weeks off all the time. When I get in truck it isn't unusual to have zero air pressure and it still starts

Yeah same with my Mack. It seeps like they all do. If anything I'm having to charge batteries but 0 PSI is never a problem other than waiting for it to build enough to move.

 

[mndriver]

Had a bad air fitting on my fan control solenoid of all things give me emission and brake faults because it was leaking that bad.

Severe enough when I got home, I had to fix it immediately as it was loosing air so fast, my brakes weren’t working correctly.

The loss of air pressure was impacting the AHI pressure regulator to not let it give 40 psi air pressure to the ahi module. This resulted in a fouled out 7th injector.

 

[Electric Chicken]

Had a bad air fitting on my fan control solenoid of all things give me emission and brake faults because it was leaking that bad.

Severe enough when I got home, I had to fix it immediately as it was loosing air so fast, my brakes weren’t working correctly.

The loss of air pressure was impacting the AHI pressure regulator to not let it give 40 psi air pressure to the ahi module. This resulted in a fouled out 7th injector.

I had an emissions issue around the same time as my fan control solenoid went out too.

I must have caught it before it had a major drivability affect because I didn't experience brake problems.

I didn't think they were related until you made this post. Maybe they weren't and it had an air leak too, which would have been fixed with solenoid replacement anyway, but they tested the solenoid as bad.

 

[mndriver]

I’d loose all my air in about 65-80 minutes.

Even with my hearing aids out, I could hear this leak.

 

[Electric Chicken]

I’d loose all my air in about 65-80 minutes.

Even with my hearing aids out, I could hear this leak.

Ohhhh. Yeah I was never that bad if I had any leak of that nature.

 

[Hammer166]

Why would a 2019 FL need air pressure to start?

I can see it needing air to MOVE if its got a automatic boat anchor tranny, but why wouldn’t it start if its low?

I'm guessing that being a roadside call, the truck rolled to the side dead, and no one thought to hit neutral before air bled off. And they won't start in gear.

 

[Electric Chicken]

I'm guessing that being a roadside call, the truck rolled to the side dead, and no one thought to hit neutral before air bled off. And they won't start in gear.

You could be right. I've never had that specific case happen. My Mack automatically goes into neutral once you pop the brakes after warning you that you're a forgetful idiot, but it's a panel button control on the dash, not a physical rotary switch on a stalk like FL. I don't remember if FL does the same thing but the physical switch would still need moved.

I do remember having a helluva time playing air pressure games constantly rotating the switch on a Cascadia back and forth to get it to engage but I didn't shut the truck off the entire time. It sorta shifted okay going down the road but somehow the fork or something wasn't working right (I can't remember and I'm not a transmission expert). I only ran 24 miles that day down and back. It was a nightmare.

 

[Electric Chicken]

So it does have auto neutral when the parking brakes are activated, but I don't know the minimum air pressure required for it to work, if any.

I would assume if you had enough service brake to get safely off the road you'd have enough to engage neutral, if air pressure is why you pulled off the road in the first place.

Moving the shifter to neutral is just an electrical thing.

 

[mndriver]

You’re not driving the engine in a Volvo / Mack.

You’re driving the transmission

The transmission controls the engine.

Check out about 1:55…



Yes, I ripped my 3.08 gears out and put 2.64 gears in. I also had it retuned for a straight 500/1850 torque from Volvo directly.

 

[mndriver]

another pointer…

Drive in “M”…

It will pull rolling hills better and shift even less.

 

[arkansas-jimmy]

I operate a roadside assistance company usually just for small cars and trucks, Sometimes I get call for the trucking companies. Which trucks and year made require some air pressure before the truck will even start. and where I can find more details how to add air to those truck so they do start.

this tread in Truck Maintenance And Repair
" 2012 FL Cascadia Air Pressure/ Transmission issue" posted Feb 25, 2017 is what I reference in my beginning thread.

 

[mndriver]

this tread in Truck Maintenance And Repair
" 2012 FL Cascadia Air Pressure/ Transmission issue" posted Feb 25, 2017 is what I reference in my beginning thread.

To truly be able to add air requires adding an air fitting to the air system with a shutoff or something to prevent loss of air when you disconnect.

Unless you are intimately familiar with truck air systems, I won’t tell you how to do that and if you were knowledgeable about them, you’d have already done it.


Bad things can happen if you suddenly apply air to a truck and you haven’t ensured it’s ready to get air.

 

[arkansas-jimmy]

yep.. I found at one time a set of adapter for adding air to truck, but cannot find that adapter set again, was a set of 4 adapters